CN1041683C - A method for eliminating acoustic echo in a communication device - Google Patents
A method for eliminating acoustic echo in a communication device Download PDFInfo
- Publication number
- CN1041683C CN1041683C CN93104986A CN93104986A CN1041683C CN 1041683 C CN1041683 C CN 1041683C CN 93104986 A CN93104986 A CN 93104986A CN 93104986 A CN93104986 A CN 93104986A CN 1041683 C CN1041683 C CN 1041683C
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- China
- Prior art keywords
- mentioned
- echo
- communication path
- code word
- radiophone
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/015—Reducing echo effects
Abstract
The process of the present invention operates on the voice codewords transmitted in a digital cellular radiotelephone environment. The process first determines if a voice is active (201) on the communications path from the base station to the radiotelephone. If a voice is present, a threshold is calculated (202). Any signals on the reverse path from the radiotelephone to the base station that are below this threshold (203) are replaced by noise that is at the same level as the ambient noise (204).
Description
The present invention relates to the communications field, particularly echo cancellation technology in the hands free communications device.
The cellular radio telephone system applies many antennas that are positioned at the entire city zone.Every pair of antenna places the central authorities of the Cellular Networks unit that is divided into six 60 ° of fan sections usually.Each fan section has the frequency of a group with low power transmissions, so that converse with movable type that is positioned at this fan section or portable radiotelephone.When radio telephone when a fan section moves to another fan section, the Automatic Frequency that just is being used is switched, so that call continues and is not interrupted.This can make the wireless telephone user in the cellular radio telephone system scope at any time all can keep in touch with the above-ground route telephone system.
The universal radiotelephone call that has caused some cities to stand to transship of the communication of this type.Sometimes, when whole frequencies are all occupied, extra user this system that is allowed for access in the time of must having frequency idle by the time.For this reason, cellular telephone industry department develops a kind of digital cellular telephone system of a new generation, and it is used time-division multiple access (TDMA) (TDMA) method and replaces existing analog system.
Tdma system is divided into a plurality of time slots with each frequency, so that a plurality of radio telephone can use a frequency simultaneously.Therefore, tdma system has been expanded the wireless telephonic quantity that can both use this radio telephone system significantly.
Mobile phone can use with a mobile phone, or uses with under the hands-free way.Mobile phone has a microphone and a loud speaker, and it is held to such an extent that converse near face.In tdma system, microphone is connected on the vocoder usually indirectly, and vocoder converts analog voice signal to code word, and code word is to represent one of speech signal to quantize parameter.
The speaker phone operational mode allows the user need not hold mobile phone can to converse in the short distance being separated by with microphone and loud speaker.Be the operation of suitable hands-free phone, the sound of the microphone of when the loud speaker sounding, must decaying.Here it is will reduce the loudspeaker sound that received by microphone, in order to avoid send back to the talker at the conversation other end.If undamped, then the caller of telephone wire one end of calling out on ground can feel an echo of the speech of hearing him.Equal voice signal turns back to former talker through this system delivery time the lag time of this echo.
Above-mentioned decay is relevant with the volume of loud speaker sounding, and attenuation may be not enough to eliminate described echo, and for this reason, radio telephone system can be provided with an Echo Canceller, with the unnecessary echo of cancellation.Yet the volume of looking the loud speaker sounding is even also may left abundant echo be heard by sense after doing like this.Therefore, need a kind of method of eliminating echo fully now.
The invention provides a kind of in order to eliminate the method for echo in the hands free communications device, above-mentioned communication equipment is conversed mutually with the base station, and have a forward communication path and a reverse link communication path from above-mentioned communication equipment to above-mentioned base station from above-mentioned base station to above-mentioned communication equipment, this method is characterized in that may further comprise the steps:
Judge on the reverse link communication path whether the echo activity is arranged; And
Replace above-mentioned echo with at least one code word that above-mentioned communication equipment produced, this code word is represented the energy and the frequency spectrum of ambient noise.
Another kind of in order to eliminate the method for echo in the hands-free radiophone, above-mentioned radiophone has: a loud speaker; A microphone is coupled with a vocoder, in order to produce code word from speech signal; And echo canceller, this radiophone communicates with a telephone-switching network on radio frequency, and a forward communication path and the reverse link communication path from above-mentioned radiophone to above-mentioned telephone-switching network from above-mentioned switching network to above-mentioned radiophone is arranged, the method is characterized in that comprising the steps:
Judge on the forward communication path whether the speech signal activity is arranged;
If the speech signal activity is arranged on the forward communication path, then be the echo code word calculated threshold on the reverse link communication path;
If the amplitude of echo code word is less than threshold value on the reverse link communication path, then the code word with the energy of representing ambient noise and spectrum component replaces above-mentioned echo code word.
The method of elimination echo of the present invention can be used in the hands free communications device, to converse mutually with other communication equipment or base station.Above-mentioned communication equipment has a forward communication path and the reverse link communication path from the hands free communications device to the base station from the base station to the hands free communications device.This method will judge at first whether echo is worked on the reverse link communication path.If have echo on this path, then replace with noise.
In one embodiment of the invention, hands free communications device is a cellular radio telephone machine.This radiophone and a base station conversation that is networked to the above-ground route telephone network.
Fig. 1 illustrates a hands-free radio telephone system of the present invention.
Fig. 2 illustrates the flow chart of signal processing of the present invention.
Echo level figure after Fig. 3 illustrates and handles with typical radio telephone Echo Canceller.
Fig. 2 illustrates echo cancellation process of the present invention.It is in the radiophone that this process is applied in that a movable type exempts from, and this telephone set is worked in digital cellular radio telephone environment.This process utilize noise replace echo can eliminate radio telephone and above-ground route telephone subscriber or and other wireless telephone users between any echo of possible dropped calls.This process relies on the work of language code word, and this code word is sent out away, and it is not an analog signal, is produced by speech coder (vocoder).
Fig. 1 illustrates a kind of typical radio telephone system, this system implementation elimination of the present invention echo process.The mobile side 120 of this system includes hands-free microphone 122 and loud speaker 121, and they are by an echo canceller 125, vocoder 130, a VSP algorithm computation device 123 and an Echo Canceller 124 and be coupled with portable transceiver 126.
The above-ground route side 110 of this system includes base station 115, base stations control terminal 116, above-ground route center telephone call office 117 and the interface circuit 118 that can directly converse with radio telephone 120.This interface circuit 118 is connected center telephone call office 117 with above-ground route phone 119.
Described processing procedure has or not voice signal movable (step 201) from what check the forward communication path.Forward communication path 101 and reverse link communication path 102 have shown bright at Fig. 1.Forward path 101 is signal direct of travels from above-ground route side 110 to radio telephone pusher side 120; Reverse path is the direct of travel of signal from radio telephone pusher side 120 to above-ground route side 110.
If do not have voice activity in the forward path 101, then processing procedure finishes (step 210).Because of not having voice activity on this path, so loud speaker 121 sounding not, microphone 122 can not pick up voice signal from loud speaker 121, does not just have echo yet.
If in forward path, detected voice activity, whether exist in order to judge echo, must determine a threshold value T (step 202).Any signal that is lower than this threshold value is considered to echo.
Threshold value T calculates by following formula:
Threshold value T=D-A
s-A
c(dB) in the formula
D is the dynamic range (dB) of voice signal;
A
sIt is the attenuation (dB) from the loud speaker to the microphone;
A
cIt is the attenuation (dB) that echo canceller is introduced.
This formula places the peak of echo with threshold value, thereby can prevent the cutting to not being any voice signal of echo.
This situation is shown among Fig. 3.Among the figure, around radio telephone ambient noise level on every side, promptly noise floor 301, are-50dB.This ground noise decays 302 by the normal attenuation process 124 of radiophone.Appearing at as shown in the figure between 0.3 second to 0.5 second is that the echo 303 that escapes from this decay rises on the noise floor 301.
Next step is to judge that whether energy on the reverse link communication path is less than threshold value T (step 203) for a method of the present invention.If echo exceeds threshold value, then processing procedure finishes (step 210), because at this moment replace the voice signal that this signal may cause cutting non-echo.If echo is lower than threshold value, then replace echo (step 204) with noise.
Use " noise " this term in order to discern among the present invention in the language code word current techique term of representing current noise substrate statistic.The statistic of current noise substrate is meant the energy and the spectrum component of current noise.On behalf of the code word of noise, these can replace with the echo code word.
The level of the noise of do replacement usefulness is identical with noise floor.So just obtain to eliminate effect disagreeable, the echo that can be heard by the above-ground route telephone subscriber, in the case, only can hear the background noise that matches with the radio telephone surrounding environment.
Claims (3)
1. one kind in order to eliminate the method for echo in the hands free communications device, above-mentioned communication equipment and a base station conversation, and have a forward communication path and a reverse link communication path from above-mentioned communication equipment to above-mentioned base station from above-mentioned base station to above-mentioned communication equipment, it is characterized in that may further comprise the steps:
Judge on the reverse link communication path whether the echo activity is arranged; And
Replace above-mentioned echo with at least one code word that above-mentioned communication equipment produced, this code word is represented the energy and the frequency spectrum of ambient noise.
2. one kind in order to eliminate the method for echo in the hands-free radiophone, and above-mentioned radiophone has: a loud speaker; A microphone is coupled with a vocoder, in order to produce code word from speech signal; And echo canceller, this radiophone communicates with a telephone-switching network on radio frequency, and a forward communication path and the reverse link communication path from above-mentioned radiophone to above-mentioned telephone-switching network from above-mentioned switching network to above-mentioned radiophone is arranged, it is characterized in that comprising the steps:
Judge on the forward communication path whether the speech signal activity is arranged;
If the speech signal activity is arranged on the forward communication path, then be the echo code word calculated threshold on the reverse link communication path;
If the amplitude of echo code word is less than threshold value on the reverse link communication path, then the code word with the energy of representing ambient noise and spectrum component replaces above-mentioned echo code word.
3. method according to claim 2, it is characterized in that described threshold value is to deduct " by the attenuation of echo canceller introducing " from " above-mentioned voice signal dynamic range and above-mentioned loud speaker are to the difference of the attenuation of above-mentioned microphone " to calculate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/873,841 US5222251A (en) | 1992-04-27 | 1992-04-27 | Method for eliminating acoustic echo in a communication device |
| US873,841 | 1992-04-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1080099A CN1080099A (en) | 1993-12-29 |
| CN1041683C true CN1041683C (en) | 1999-01-13 |
Family
ID=25362435
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN93104986A Expired - Lifetime CN1041683C (en) | 1992-04-27 | 1993-04-26 | A method for eliminating acoustic echo in a communication device |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US5222251A (en) |
| JP (1) | JP2926989B2 (en) |
| CN (1) | CN1041683C (en) |
| BR (1) | BR9305471A (en) |
| CA (1) | CA2102504C (en) |
| FR (1) | FR2690581B1 (en) |
| GB (1) | GB2271698B (en) |
| MX (1) | MX9302412A (en) |
| WO (1) | WO1993022844A1 (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5668871A (en) * | 1994-04-29 | 1997-09-16 | Motorola, Inc. | Audio signal processor and method therefor for substantially reducing audio feedback in a cummunication unit |
| IL115892A (en) * | 1994-11-10 | 1999-05-09 | British Telecomm | Interference detection system for telecommunications |
| US5835851A (en) * | 1995-01-19 | 1998-11-10 | Ericsson Inc. | Method and apparatus for echo reduction in a hands-free cellular radio using added noise frames |
| FI110826B (en) * | 1995-06-08 | 2003-03-31 | Nokia Corp | Eliminating an acoustic echo in a digital mobile communication system |
| FI961567A (en) * | 1996-04-10 | 1997-10-11 | Nokia Telecommunications Oy | Noise suppression in an analog mobile communication system |
| FI961568A (en) * | 1996-04-10 | 1997-10-11 | Nokia Telecommunications Oy | Discontinuous transmission in an analog mobile communication system |
| SE513672C2 (en) | 1997-09-01 | 2000-10-16 | Ericsson Telefon Ab L M | Method and apparatus for suppressing echoes |
| US6415029B1 (en) * | 1999-05-24 | 2002-07-02 | Motorola, Inc. | Echo canceler and double-talk detector for use in a communications unit |
| DE19935808A1 (en) | 1999-07-29 | 2001-02-08 | Ericsson Telefon Ab L M | Echo suppression device for suppressing echoes in a transmitter / receiver unit |
| FR2828327B1 (en) * | 2000-10-03 | 2003-12-12 | France Telecom | ECHO REDUCTION METHOD AND DEVICE |
| US8949120B1 (en) | 2006-05-25 | 2015-02-03 | Audience, Inc. | Adaptive noise cancelation |
| US8488805B1 (en) * | 2009-12-29 | 2013-07-16 | Audience, Inc. | Providing background audio during telephonic communication |
| US9640194B1 (en) | 2012-10-04 | 2017-05-02 | Knowles Electronics, Llc | Noise suppression for speech processing based on machine-learning mask estimation |
| US9536540B2 (en) | 2013-07-19 | 2017-01-03 | Knowles Electronics, Llc | Speech signal separation and synthesis based on auditory scene analysis and speech modeling |
| WO2016033364A1 (en) | 2014-08-28 | 2016-03-03 | Audience, Inc. | Multi-sourced noise suppression |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3991287A (en) * | 1975-04-24 | 1976-11-09 | Bell Telephone Laboratories, Incorporated | Digital echo suppressor noise insertion |
| CA1233925A (en) * | 1985-05-10 | 1988-03-08 | Gordon J. Reesor | Digital loudspeaking telephone |
| US4843621A (en) * | 1987-04-24 | 1989-06-27 | Motorola, Inc. | Speakerphone using digitally compressed audio to detect acoustic feedback |
| US4829523A (en) * | 1987-11-18 | 1989-05-09 | Zenith Electronics Corporation | Error masking in digital signal transmission |
-
1992
- 1992-04-27 US US07/873,841 patent/US5222251A/en not_active Expired - Lifetime
-
1993
- 1993-03-11 BR BR9305471A patent/BR9305471A/en not_active IP Right Cessation
- 1993-03-11 JP JP5519245A patent/JP2926989B2/en not_active Expired - Fee Related
- 1993-03-11 WO PCT/US1993/002153 patent/WO1993022844A1/en active Application Filing
- 1993-03-11 GB GB9323335A patent/GB2271698B/en not_active Expired - Lifetime
- 1993-03-11 CA CA002102504A patent/CA2102504C/en not_active Expired - Fee Related
- 1993-04-26 CN CN93104986A patent/CN1041683C/en not_active Expired - Lifetime
- 1993-04-26 MX MX9302412A patent/MX9302412A/en unknown
- 1993-04-27 FR FR9304929A patent/FR2690581B1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| BR9305471A (en) | 1996-01-09 |
| JPH06508256A (en) | 1994-09-14 |
| CA2102504A1 (en) | 1993-10-28 |
| CA2102504C (en) | 1997-04-22 |
| GB2271698A (en) | 1994-04-20 |
| JP2926989B2 (en) | 1999-07-28 |
| GB2271698B (en) | 1995-11-01 |
| WO1993022844A1 (en) | 1993-11-11 |
| FR2690581B1 (en) | 1994-12-16 |
| US5222251A (en) | 1993-06-22 |
| CN1080099A (en) | 1993-12-29 |
| GB9323335D0 (en) | 1994-02-09 |
| FR2690581A1 (en) | 1993-10-29 |
| MX9302412A (en) | 1993-10-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C06 | Publication | ||
| PB01 | Publication | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| ASS | Succession or assignment of patent right |
Owner name: MOTOROLA MOBILE CO., LTD. Free format text: FORMER OWNER: MOTOROLA INC. Effective date: 20101230 |
|
| C41 | Transfer of patent application or patent right or utility model | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20101230 Address after: Illinois Instrunment Patentee after: Motorola Mobility LLC Address before: Illinois Patentee before: Motorola Inc. |
|
| C17 | Cessation of patent right | ||
| CX01 | Expiry of patent term |
Expiration termination date: 20130426 Granted publication date: 19990113 |